In order to ignite the fuel in the combustion chamber of a gas turbine engine, an ignitor plug is arranged to extend into the chamber. The plug extends through a hole in the combustor casing. During operation of the engine, the combustor casing moves relative to the combustion chamber, because of the different thermal expansions. The ignitor hole needs to be larger than the ignitor plug to compensate for this movement.
A seal is used to overcome the problem of leakage through the hole. The seal is mounted in a tower arrangement extending radially outwardly from the combustor. A ring welded on to the top of the tower secures the seal to the tower.